Re: Is Oscar 100 visible?

Nicholas Shaxted

Before anyone asks the question I can say that a number of us have looked into the possibility of back scatter from geostationary satellites. Admittedly it was a long time ago but the general conclusion was that given power levels and limited amateur dish sizes one would still be more than 10dB (nearer 20dB) below successful detection.

Calculations did not take into corner reflections or other unquantifiable reflections.


Since the work was done probably over 10 years ago, power levels at 9cm through to 3cm have improved (cheaper). Signal recovery from noise techniques have also improved (a little).


The implication is that the gap has narrowed…


As for optical visibility, you can over a period of nights take images with a relatively small telescope and see how well a geostationary satellite is kept in its (I think, 15km x 15km) box.


Incidentally the only workable forward scatter path using a geostationary satellite I found was from Southern Spain/Portugal to Australia so essentially amateurs are limited to exploiting backscatter.


If we do have anyone with spare time, try looking for Snoopy





Nick – g4ogi


From: On Behalf Of Neil Smith G4DBN via Groups.Io
Sent: Friday, June 28, 2019 7:34 PM
Subject: Re: [UKMicrowaves] Is Oscar 100 visible?


It is possible to see flares from geostationary satellites, but it is not easy.  Photos of the ISS are often taken from the ground with serious optics, but that is from less than 1000km, and the ISS is huge.

There is a time-lapse at showing a whole set of geo sats against the sky background. I haven't seen anyone reporting seeing a flare from QO100 (yet). I'm more into Iridium and LEO flares, which are way brighter.

The size of QO100 at 40000km is around 0.03 arcseconds, and the best seeing from ground level with a very big (read "expensive") scope is likely to be well over an arcsecond.  Even from the big scopes on top of mountains, you would struggle to get better than 0.4 arcseconds.

Specular reflections from the panels on QO100 would appear to be the same size as the point-spread function of the lens, same as a star.  It is effectively a point-source with no lateral dimensions, so although some of the satellites flares from geos are bright enough to see with dark-adapted eyes and no scope/bins, you stand zero chance of imaging the thing from the surface of the earth other than as a point spread by your imaging system.

Using Hubble, the resolution would be around 0.12 arcseconds, so still impossible to resolve any detail.  Definitely worth checking the geometry and seeing if there is an optimal time of year to see panel reflections.

Neil G4DBN

On 28/06/2019 18:09, KENT BRITAIN wrote:

You are trying to see a containerized cargo container at 40,000 km.

BIG binoculars!


With luck you might get a time with the sun reflects at just the right angle,

they call it a flare.      Good luck!  WA5VJB


On Friday, June 28, 2019, 11:59:44 AM CDT, John E. Beech <john@...> wrote:



Hi All,

        This may or may not be relevant to this group, but is Oscar 100 ( or any geostationary satellite) visible at night through binoculars? ( Assuming a clear ,dark sky) Has anyone from this group tried looking at it?


de John G8SEQ




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